Add task 2 code

Signed-off-by: Warrick Lo <wlo@warricklo.net>

1 files changed, 50 insertions, 6 deletions

diff --git a/task2/fillscreen.sv b/task2/fillscreen.sv
index 323e7a5..de7a928 100644
--- a/task2/fillscreen.sv
+++ b/task2/fillscreen.sv
@@ -1,7 +1,51 @@
-module fillscreen(input logic clk, input logic rst_n, input logic [2:0] colour,
-                  input logic start, output logic done,
-                  output logic [7:0] vga_x, output logic [6:0] vga_y,
-                  output logic [2:0] vga_colour, output logic vga_plot);
-     // fill the screen
-endmodule
+module fillscreen(clk, rst_n, colour, start,
+	done, vga_x, vga_y, vga_colour, vga_plot);
 
+	input logic clk, rst_n, start;
+	input logic [2:0] colour;
+	output logic done, vga_plot;
+	output logic [2:0] vga_colour;
+	output logic [6:0] vga_y;
+	output logic [7:0] vga_x;
+
+	logic clear;
+	logic [6:0] y_next;
+	logic [7:0] x_next;
+
+	assign vga_colour = clear ? 3'b000 : vga_x[2:0];
+	assign vga_plot = clear || (start && ~done);
+	assign x_next = vga_x + 1;
+	assign y_next = vga_y + 1;
+
+	always_ff @(posedge clk) begin
+		if (~rst_n) begin
+			done <= 1'b0;
+			vga_x <= 8'b0;
+			vga_y <= 7'b0;
+			/* Start clearing the screen. */
+			clear <= 1'b1;
+		end
+
+		if (clear || (start && ~done)) begin
+			if (vga_y < 120) begin
+				/* Check for one column less since it takes
+				 * one clock cycle to reset and increment. */
+				if (vga_x < 159)
+					vga_x <= x_next;
+				else begin
+					vga_x <= 8'b0;
+					vga_y <= y_next;
+				end
+			end else begin
+				if (clear)
+					clear <= 1'b0;
+				else
+					done <= 1'b1;
+				vga_x <= 8'b0;
+				vga_y <= 7'b0;
+			end
+		end else if (~start && done)
+			done <= 1'b0;
+	end
+
+endmodule: fillscreen